Disk drives may use a single stage actuator for positioning the read/write head of a particular slider relative to the desired track of the corresponding data storage disk. One common way to provide this single stage positioning is through the voice coil motor. Dual stage positioning approaches are at least being considered in the disk drive industry. Such a dual stage approach may use both the voice coil motor (e.g., a first stage actuator), as well as what is commonly referred to in the art as a microactuator or a slider positioner (e.g., a second stage actuator) that is typically mounted on a deflectable flexure tongue. This microactuator may be in the form of a U-shaped frame having a base and a pair of deflectable arms that each cantilever from the base. The slider is disposed between these arms in spaced relation to each arm and the base. A “spot” of epoxy attaches the slider to each of the arms. One or more actuating elements (e.g., multi-layer piezoelectric structures) are mounted on the flexure tongue and engage the outside of each of the arms. Activation of the piezoelectric elements(s) associated with one of the arms will exert a force on the corresponding arm that deflects at least this arm, and thereby changes the position of the slider and its read/write head.
The microactuator frame may be made from a relatively brittle material, for instance a ceramic. A slot may be formed in the frame adjacent to each arm and filled with an appropriate epoxy to reduce the stresses that are concentrated at these two corners and also to structurally reinforce the frame. It is difficult to fill these slots to the appropriate level, which adversely affects the yield of the microactuator/slider assembly. Under-filling either slot may not sufficiently reduce the potential for cracking of the microactuator frame at the junction of an arm with the base, either during operation of one or both of the piezoelectric elements or as a result of exposure to a shock event. Over-filling of either slot may result in epoxy being disposed on the distal end of the portion of the base that is disposed between the two deflectable arms. This may present a clearance issue when the slider is disposed in the space between the arms and the base. That is, typically there is only a small gap between the slider and the portion of the base that is disposed between the arms. Having epoxy in this gap may adversely affect the ability to dispose the slider in the correct position, the movement of the slider by the microactuator, or both.